The companies also cooperate on a compound similar to regorafenib called Nexavar.

Regorafenib had become a bone of contention between Bayer and Onyx in 2009, when Onyx said the compound should be treated as an offshoot from their joint Nexavar project while Bayer laid sole claim to the drug but the dispute has been settled.

Both Nexavar and regorafenib are so-called multikinase inhibitors that quell cancer cell growth and prevent new blood vessels that could feed tumors.

Bayer, the inventor of Aspirin which also makes plastics and pesticides, is also testing regorafenib against a number of tumor types including kidney cancer.